Retina, Pixel Art, and co-ordinates

Questions
1

Hi. I’m making an app that uses pixel art graphics, and I want to be able to place sprites on an exact pixel on the screen.

This works great on a non-Retina iPad. I use “noSmooth()” and “spriteMode(CORNER)” in set up, and set the position of a sprite to an exact coordinate. Then I scale everything by 4 (using “scale(4,4)”) at draw, and I get that nice, chunky, pixel-perfect art style I’m after.

On Retina iPad, it doesn’t go so well. I can use “scale(8,8)”, but because of the way Codea handles Retina, my alignments are now off by a factor of 2. A button that was 70 pixels from the left is now 140 pixels from the left.

One way to fix this is to set all my positions as something like “70/ContentScaleFactor” so on Retina iPads, where the ContentScaleFactor is 2, the alignments are halved (to 35, then doubled back up to 70).

That works, but I feel like that’s not particularly sensible code. Plus, I have to write that in every time I want to place a sprite.

Is there something I can to do to surpress Codea’s position doubling on a Retina device? Or a way to half the x and y values of everything at draw time?

Any ideas welcomed!

Thanks

2

.@britishgaming perhaps I’m missing something, but shouldn’t you get the same result with the same code on retina and non-retina devices?

For example the following code draws the sprite in the exact same physical location and size on both retina and non-retina screens:

scale(4,4)
noSmooth()
spriteMode(CORNER)
sprite("Tyrian Remastered:Bad Case", 50, 50)

Now I understand that in the retina case, the sprite will really be rendered twice its size and at x=100, y=100, but that will look identical to the non-retina version. That is, they will occupy the same physical area if you were to hold two iPads, retina and non-retina, next to each other.

Am I misunderstanding what you are trying to do? Do you want the exact same appearance on both retina and non-retina displays? In that case, the same code should produce the same result.

And just as a sanity check: you don’t have @2x graphics that are identical resolution to your non-@2x graphics?

3

Hey Simeon - ah, I think your sanity check was completely - and embarrassingly - correct.

When I imported my sprites I had the Retina box checked, which seems to be the cause of the trouble (the dimensions in the Edit Image window were halved). I re-imported, with Retina unchecked, and now it’s the exact same on both my iPad 3 and mini. Perfect.

Whoops! Thanks so much for your help.

4

Glad to have helped.

How is Codea on an iPad mini? I haven’t had an opportunity to try it, and was afraid some of the buttons might be too small.

5

I’d say it’s fine as it is! I’m only using it to test as a non-Retina device, but just had a fiddle and all the major buttons are easy to tap. Shouldn’t cause any problems at all.